25 Jun 2014

Heavy showers this weekend: wellies galore at Glastonbury

June so far has seen high pressure grace our shores for much of the time, giving lots of settled weather, warmth and pleasant spells of summer sunshine.

However, fortunes are set to change this weekend, with low pressure drifting across us, bringing many places a change to heavy downpours.

This means that both the Glastonbury Festival and Wimbledon tennis will see some rain at times, bringing the threat of mud and interruptions to play. 


Why the change from high to low pressure?

Up to now, June has been dominated by a blocking high pressure in the atmosphere, with the jet stream generally nowhere near the UK.

This high pressure has acted as a defender of rain-bearing weather systems, so aside from a few showers or cloudier skies, most of this month has seen sunshine and warmth.

In the coming days, the jet stream is going pick up speed and move close enough to spawn an area of low pressure that will drift across the UK through Friday and the weekend.

The area of low pressure is going to be moving slowly, which means that it’ll hang around for quite a few days before moving away.

Why is the low pressure moving so slowly?

The easiest way to explain this is to use an analogy of a spinning top on a conveyor belt in a supermarket, with the low_pressure_MO_wpconveyor belt being the jet stream and the spinning top the area of low pressure.

Normally, the jet stream acts as a swift conveyor belt, pushing low pressure along, keeping it moving.

However, in summer the jet stream is generally weaker and moves more slowly than at other times of the year. As a result, areas of low pressure can occasionally stick around for longer, resulting in more days of heavy showers.

What to expect this weekend

There is still some uncertainty with the precise detail, but at the moment, it looks like England and Wales will be most unsettled.

Showers or longer spells of rain are likely, with possible thunder. However, in between the downpours, there will be spells of sunshine.

Scotland and Northern Ireland will have the best of the weather this weekend, with a lot of dry weather, sunny spells and just a few showers.

One universal theme is that it will be cooler and fresher than the past week. Temperatures will be around 14-18C in the northern half of the UK, with 16-21C likely elsewhere.

Don’t forget, you can get the latest forecast on the Channel 4 Weather website. I’ll also be posting regular updates on Twitter – @liamdutton

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